Refastenable mechanical fastening systems are well known in the art. Typically such fastening systems involve two major components, a prong which is joined to a substrate and engages a complementary second component, a receiving surface. The receiving surface typically comprises one or more layers of strands or fibers.
A projection of the prong of the mechanical fastening system, typically referred to as the engaging means, penetrates the receiving surface and engages or intercepts strands or fibers of the receiving surface. The resulting mechanical interference and physical obstruction prevent removal of the prong from the receiving surface until separation forces exceed either the peel or the shear strength of the fastening system.
Oftentimes one skilled in the art wishes to select or tailor the fastening characteristics of the mechanical fastening system to the desired application for the mechanical fastening system. In certain applications the shear strength of the fastening system becomes important (if not critical) and the designer may wish to tailor the shear strength of the mechanical fastening prong to the needs of such applications.
For example, refastenable mechanical fastening systems may be used in conjunction with disposable absorbent articles such as diapers. U.S. Pat. No. 4,846,815, issued Jul. 11, 1989 to Scripps discloses a diaper having a refastenable fastening device which provides resistance to commonly encountered shear stresses and which is comfortable and skin friendly to the wearer. U.S. Pat. No. 4,869,724, issued Sep. 26, 1989 to Scripps discloses a disposable absorbent article with adhesive tape tabs and refastenable mechanical fasteners used in conjunction with one another to provide for refastening of the disposable absorbent article about the wearer and convenient disposal of the diaper after it has become soiled.
If the refastenable mechanical fastening system is used in conjunction with a disposable absorbent article, such as a diaper, a certain minimum shear strength is necessary to minimize the chances of the mechanical fastening system becoming detached during wear, thus allowing the garment to possibly loosen or even fall off the wearer. This occurrence increases the likelihood of the absorbent garment not properly containing bodily discharges intended to be absorbed by the disposable absorbent article.
If the disposable absorbent article is an adult incontinence product, refastenable mechanical fastening systems may likewise be advantageously utilized, as disclosed in commonly assigned U.S. patent application Ser. No. 07/382,157, Issue Batch No. F40, filed Jul. 18, 1989, in the names of Gipson et al. However, contrary to the need, disclosed above, for the fastening systems to maintain a certain minimum shear strength, a mechanical fastening system used in conjunction with an adult incontinence product may need to have only a certain maximum shear strength. The difference occurs because the wearer may be of limited manual strength or dexterity, and if the shear strength of the fastening system is too great, the wearer may not be able to conveniently remove the disposable absorbent garment to inspect for soiling or for routine changing of the garment.
In yet another application, it may be desirable to have a mechanical fastening system which allows for some slippage of the prong, relative to the receiving surface, in a direction generally parallel the plane of the receiving surface and the direction in which fastening engagement is desired. Such lateral slippage produces a fastening system which is somewhat adjustable in the relative position of the prongs on the receiving surface while the two components are fastened together.
Other characteristics, such as the structural characteristics or the geometry, of the mechanical fastening systems may also be important. One skilled in the art may also wish to tailor these characteristics of the fastening system. For example, the lateral projection of the prongs may be tailored to a value which makes the prongs complementary to a particularly desired receiving surface. Another structural characteristic, the included angle of the prong relative to the substrate, influences the depth the prong penetrates the receiving surface. Thus, the designer may also wish to tailor this characteristic of the geometry of the fastening system, commensurate with the layers and the fiber or strand strength of the receiving surface and the desired shear strength of the fastening system.
Particularly, it has been found that there is a definite relationship between the included angles of the prongs relative to the plane of the substrate and the shear strength of the fastening system. Further, there is a relationship between certain parameters of the manufacturing process and the included angles of the prongs resulting from such processes.
Accordingly, it is an object of this invention to provide a process for conveniently adjusting tailoring the fastening characteristics, particularly the shear strength of mechanical fastening prongs, as the mechanical fastening system is produced. It is also an object of this invention to provide a process for adjusting the lateral projections of mechanical fastening prongs and the included angles of mechanical fastening prongs relative to the substrate during production of the mechanical fastening system. It is finally an object of this invention to provide a mechanical fastening prong which may laterally slip parallel to the plane of the receiving surface after engagement has taken place and while the mechanical fastening prong and receiving surface are fastened together.